Lincoln was not -in- the Illinois legislature in 1857, so I don't know why he would be making a speech there.
Lincoln never said that blacks were racially inferior to whites (or anyone else). He avoided declaring on that very thing and you can't quote him as saying that.
He -did- say that blacks were socially inferior to whites, and that would be hard to deny.
But I see the "freeze" is on again. You want Lincoln considered on only a partial record. He did say (And I quoted him -- which you don't bother to do) that black soldiers seemed as good as any. And he clearly favored the vote for black soldiers.
Walt